Belgian researchers at ICTEAM have announced a Multipath TCP (MPTCP) demonstration that's routed 50 Gbps of traffic across multiple different paths.
While there wouldn't be much to crow about doing this at the physical layer, the ICTEAM researchers have squeezed this performance out of a system that needs to make various kinds of upper-layer decisions about congestion windows and route paths fast enough to keep up with the underlying Ethernet links.
The experimental setup was straightforward enough: two HP DL 380p G7 machines configured with three dual-port 10 Gbps Intel NICs. The test machines were running Linux and hosting a Multipath TCP implementation created by ICTEAM. Netperf opened a single TCP connection between the two servers, and in the video below, the researchers demonstrate the scaling-up of performance, starting with a single NIC and enabling the multipath stack on the additional interfaces.
Of course, if all you needed was a fast LAN connection and nothing else, then Ethernet-level link aggregation would suffice. The point of multipath TCP is to make better use of routed links.
For background, this paper from the Internet Society explains that unmodified, TCP's routing protocols decide on the best path at the beginning of a session, and after that, they “aren't very good” at selecting alternative paths. The multipath modification creates a congestion window for each path available for a session, while trying to avoid problems like link oscillations and packets arriving out of order.
As the ICTEAM researchers explain, MPTCP also presents a standard TCP socket API to the application.
What's impressive in the Belgian demonstration is that the researchers have been able to get the higher-layer operations happening fast enough to realise most of the capacity provided by the six Ethernet ports available.
While the Belgian demonstration is looking at how MPTCP could be used in data centres, the researchers note other applications of the protocol could include helping 3G-WiFi handover happen without upsetting the applications, or even for assisting Ipv4/v6 coexistence. ®